What is $$\tan \left\{ {2{{\tan }^{ - 1}}\left( {{1 \over 3}} \right)} \right\}$$ equal to?

What is the value of $${\sin ^{ - 1}}{4 \over 5} + {\sec ^{ - 1}}{5 \over 4} - {\pi \over 2}$$ ?

If $${\sin ^{ - 1}}{{2p} \over {1 + {p^2}}} - {\cos ^{ - 1}}{{1 - {q^2}} \over {1 + {q^2}}} = {\tan ^{ - 1}}{{2x} \over {1 - {x^2}}}$$, then what is x equal to?

If 4 sin^-1 x + cos^-1 x = π, then what is sin^-1 x + 4 cos^-1 x equal to?